[U-Boot-Users] [PATCH] ppc4xx: Add dcache_enable() for 440

[Wolfgang Denk <wd@denx.de>]

Dear Stefan,

in message <200804210729.53635.sr@denx.de> you wrote:
>
> > I don't like to see these either, but it's better than lying in the
> > face of the user.
> 
> Please note that it is not so easy on 440 to even define *what exactly* the
> functions/commands d/icache_en/disable mean. This is because 440 has MMU 
> support and we can have different cache setups for all TLB entries. So to 
> which TLB entries should these functions refer? Just those mapping SDRAM? 
> And/or FLASH? And/or internal SRAM? ...

You are the 440 expert, not me :-)

> > > you are you asking for additional changes too. Are you asking me to
> > > remove (a) all dummy cache entries or (b) to support *real* cache suppo> rt
> > > functions for 440? (a) would lead as explained above to bigger code
> > > changes in the common code and (b) is extremely difficult and I just ha> ve
> > > no time for such a thing currently.
> >
> > Yes, let's do either (a) or (b). There is no other choice.
> 
> From my point of view, both "solutions" should not be done outside of a 
> merge-window. I'll try to find some time to implement on of those options in 
> the next weeks. But perhaps somebody else has more "free time" and sends 
> patches to implement (and test) this stuff.

I agree that it is probably not  possible  to  fix  this  right  now,
especially  since the actual problem is older, it just became visible
now.

But I insist that this must be fixed  for  the  next  release  -  and
actually it seems to be a good thing to really enable the instruction
cache  -  this would allow to speed up booting on 440 systems quite a
bit.

> > This still leaves the problem of the current "implementation" of  the
> > other  stubs. Please note that as is, we even have *random* behaviour
> > of the code, as the  functions  are  supposed  to  return  the  cache
> > status, but no return value gets loaded.
> 
> I don't see such a problem with *random* behavior. d/icache_status return 0 on 
> 440.

Ah, you are  right.  I  thought  that  the  {i,d}cache_{en,dis}able()
functions  returned a status, but they are indeed void. Sorry for the
false alarm.

Best regards,

Wolfgang Denk

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